Variometer for wireless receiving sets



F. C. HUTCHISON VARIOI BTER FOR WIRELESS RECEIVING SETS Filed June 15, 1922 June 15 1926.

I 35 coils have customarily been Patented June 15, 1926.

PATENT OFFICE.

FRANK C HU'IGHISON, OF, III TNEAPOLIS, MINNESOTA.

VABIOIETEB I03 WIRELESS RECEIVING SETS.

Application filed June 15, 1922. Serial {0. 568,454.

, My invention has for its particular object the provision of an improved electromagnet tuning instrument for wireless receiving sets, said tuning instrument being of the B type generally designated as a variometer. As is known, a variometer is a type of tuning coil in which a plurality of coils connected in series are rotatably mounted for adjustments to thereby va the relative positions of the north and sout poles of sand 'magnets. It is also known that such adjustments of the magnets in respect to the relative positions of the north and south poles, would serve to tune the receiving set for difi'erent wavelengths.

In the hitherto commercial variometer, one coil called the rotor has been mounted for angular rotary adjustments within the other coil called the stator, and each of said coils has had a large number of convolutions or turns. When two variometer coils are. ositioned with the north end of one at the south end of the other, the total magnetism of the two will be zero, while if they are turned with the r north poles in the same direction and their south poles in the same direction, the magnetism of the one will assist the magnetism of the other. These conditions are utilized in tuning because, other things bem equal,

the stron er the magnetism about t e tuning coil, t e greater will be the wave length to which it will respond.

In the commercial variometer, both. of the iven'a large number of turns so as to give t e instrument the desired and necessary range of adjustment in tuning, but it has followed that in such arrangements there has been great difliculty in obtaining the desired close adjustments so that, frequently, it has been imossible to keep thevariometer from passin the position for the selection of the r:-

quired wave length and, for that reason, it

has been frequently impossible to tune My invention remedies the above defect and consists in the, provision of a differential multiple variometer. More definite y.

stated, the complete variometer involves two pairs of varlometer coils connected in series, the one pair of coils having a relatively very large number of turns serving to adjust for range and the other pair ofcoilshaving a relatively very small number of turns and 5 serving to adjust for-extreme accuracy or what may be termed micrometer degree of variation of wave length. In carrying 1 this invention into commercial form, I pro vide -three spools, the first of which is fixed, the .second of which is mounted to rotate within the first and the third of which is mounted to rotate within the second; the mainvariometer coils are wound, one on the interior of the fixed first spool and the other on the exterior of the rotarysecond spool, while the auxiliary coils are wound, one within the rotary second spool and the other on the exterior of the thlrd and relatively small rotatably mounted interior spool.

With the above general statements made, I will now describe more in detail a commercial embodiment of my invention, which is illustrated in the accompanying drawings, wherein like characters indicate like 7 parts throughout the several views.

Referring to the drawin s:

Fig. 1 is a front elevation showing the dials and operatingknobs, which may be and preferably are used in connection with 00 my improved variometer; v

F ig, 2 is a view partly in elevation and partly in vertical section on the line 2-2 of Figrl, showing the improved variometer;

Fig. 3 is a horizontal section taken ap- 85 proximately on the line 33 of Fig. 2, some parts being shown in full;

Fig. 4 is a vertical section taken on the line 4-4 of Fig. 3;

Fig. 5 is a diagrammatic view illustratin 00 the wiring of the improved variometer an its connection to a wireless receiving set of well known commercial form; and

Fig. 6 is a fragmentary horizontal section illustrating a slightly modified form of the 06 im roved variometer. I

' ferr' first to the construction illus trated in Figs. 1 to 5, inclusive, the numeral 7 indicates the lirst or fixed cuter spool, the numeral 8 indicates the second or relatively large rotary spool and the numeral 9 indicates the third or small interior spool, which spools are made of non-conductive and non-magnetic material, such as wood. The spool 7 is formed with an internal spherical surface, against which the stationary member 10 of the main variometer coils is secured in the customary way. The spool 8 has a spherical outer surface on which the movable varioineter coil 11 is secured, also in the customary way. In carrying out my invention, the spool 8 is formed with a hollow spherical inner surface 12 to which the relatively fixed auxiliary variometer coil 13 is secured. The small inner spool 9 has a spherical outer surface on which the relatively movable auxiliary variometcr coil 14 is secured. With the above arrangement,the coils 10 and 11 are spaced but closely positioned and the auxiliary coils 13 and 14 are also spaced but closely positioned.

The main spool 8 is provided with axially aligned outwardly projecting tubular shafts 15 and 15, which, as shown, are journaled in bearing plates 16 secured to the opposite sides of the fixed spool 'i'. The shaft 15 is also shown as journaled in one side of a casing 17 and secured to the outer end thereof is a dial 18 and a main operating knob 19. The small inner spool 9 is secured to axially spaced but axially aligned small shafts 20 and 2O that extend through and are journaled in the shafts 15 and 15, respectively. The shaft 20, at its outer end, is provided with a relatively small so-called auxiliary knob 21. Adjustments of the spool 8 are, of course, made by manipulation of the main knob 19, and adjustments of the small inner spool 9 are made by manipulation of the auxiliary knob 21.. In the preferred arrangement, the dial 18 is provided with a light spring 22 that frictionally engages the plate 17 and serves to prevent the spool 8 from being accidentally moved or from being moved when the inner spool 9 is adjusted. The secondary knob 21 is also preferably provided with a spring finger 23 that frictionally engages the adjacent end of the main knob 19 and produces sufficient friction to cause the inner spool 9 to normally move wit-h the spool 8. The spring finger 23 is also preferably used as a pointer for cooperation with a dial or graduations 24 marked on the end of the knob 19.

As already stated, the coils 10, 11, 13 and 14 are connected in series and, as shown, this is accomplished as follows: The numerals 25 and 26 indicate the direct current leads of the wireless receiving set. The lead 25 is connected to one terminal 10 of the main coil 10 and the other terminal 10 of said coil is connected to the tubular shaft 15 Said shaft 15 at its inner and outer ends, is provided with insulating portions 15' that directly engage the shaft 20 but electrically insulate the two shafts, one from the other The tubular shaft 15, near its inner portion, is electrically connected to one terminal 11 of the relatively movable main coil 11, and the other terminal 11' of said coil 11 is connected to one terminal of the auxiliary coil 13, the other terminal 1?," of which coil 13 is electrically connected to the tul'uilar shaft 15, (see Fig. 3). Th shaft 20 is electrically connected to the shaft 15 and its inner extremity is electrically connected to one terminal 14 of the auxiliary coil 14', the other terminal 14" of said coil 14 being electrically connected to the shaft 20. The outer end of said shaft 2.0 is connected by a wire 27 to the lead 26. The wires 19 and 27 have sufficient slack to permit complete oscillatory rotations of the spools 8 and 9 in respect to each other and in respect to the fixed spool 7. All of the wires noted are covered with suitable insulation.

The construction illustrated in Fig. 6 differs from that above des-ribed only in the fact that the inner surfaces of the fixed spool 7 and of the adjustable spool 8' are cylindrical. This construction does not give as high etliciency as the spherical construe than above described, but has the advantage that said spools do not need to be made in sections but can be made each of an integral member.

In the arrangement ab ve described, it is evident that the several coils 10, 11, 13 and 14 are always connected in series, regardless of adjustments. It is also evident that, by manipulation of the knob 1.9, the instrument may be quickly brought approximately into tune in the customary way and that the final accurate adjustment may be made by manipulation of tin auxiliary knob 21, which in'iparts movements to the small inner spool 9 and the coil carried thereby. In practice, it will frequently happen that in adjusting for tuning by mwnipulation of the knob 19, there will be a clicking or sound indication indicating that the adjustment has just passed the proper tuning pitch and, when this takes place, the main knob should be stopped or set and the final selecting adjustment should be made by manipulation of the knob 21.

In actual practice, I have found this improved tuning instrument or differential variometer to be highly satisfactory for the purposes had in view and to make the most accurate tuning adjustments an exceedingly easy matter. The manner in which the main and auxiliary coils, which make up the differential variometer, are assembled together, not only brings them into the most compact form but makes it feasible to assofixed outer main spool, a cooperating hollow main spool rotatably mounted Within said fixed spool, a relatively small auxiliary spool rotatably mounted 1n said rotary main spool, cooperating main variometer coils secured one to the interior of said fixed main spool and the other to the exterior of said rotary main spool, and auxiliary variometer coils of relatively low inductance secured one to the interior of said rotary main spool and the other to the exterior of said inner auxiliary spool, the said coils belng connected 1n series.

In testimony whereof I afiix my signa- 2c ture.

FRANK G. HUTCHISON. 

